Gal4-DNA-binding domain fusions ("baits") are expressed in PJ69-4alpha:
MATalpha trp1-901 leu2-3,112 ura3-52 his3-200 gal4(deleted) gal80(deleted) LYS2::GAL1-HIS3 GAL2-ADE2 met2::GAL7-lacZ

GAL4 activation domain fusions ("preys") are expressed in PJ69-4alpha:
MATa trp1-901 leu2-3,112 ura3-52 his3-200 gal4(deleted) gal80(deleted) LYS2::GAL1-HIS3 GAL2-ADE2 met2::GAL7-lacZ

Both strains are identical except for the mating type. PJ69-4alpha was constructed by Phil James et al. (1996) and is described in:
James, P., Halladay, J. & Craig, E. A. (1996) Genomic libraries and a host strain designed for highly efficient two- hybrid selection in yeast. Genetics 144: 1425-1436